In situ Raman spectroelectrochemical study of self-doped polyaniline degradation kinetics

The kinetics of electrochemical degradation for a self-doped sulfonated polyaniline derivative (a copolymer of aniline and m-aminobenzenesulfonic acid) has been studied with in situ Raman spectroscopy. It has been shown that the degradation proceeds faster in more acidic solutions. From the data obtained, first-order degradation rate constants have been calculated. Within the solution pH range of 0.5-9.0, first-order rate constants thus obtained vary, respectively, between (6.6 +/- 0.8) x 10(-4) s(-1) and (0.8 +/- 0.1) x 10(-4) s(-1) for electrode potential of 0.8 V vs. Ag/AgCl. A linear correlation between the degradation rate constant and solution pH has been found: log k = log k(0) + a.pH, where k represents rate constant at any pH (expressed in s(-1)), k(0) is the rate constant for pH 0, log k(0) = -3.09, and a = -0.11 is the slope of (log k, pH) dependence. (C) 2006 Elsevier B.V. All rights reserved.